The present invention relates to a process for conditioning standing and flowing water systems using polysuccinimide and novel conditioning agents based on polysuccinimide (PSI) or its partial hydrolysates in combination with fatty acids or their derivatives for preventing deposits which form in standing or flowing water systems owing to hardness-forming ions.
For the purposes of the present invention, flowing water systems are construction drainage systems or drains, but also injection water in the exploration of raw materials, in particular oils or natural gases, particularly preferably in “squeeze” operations in oil extraction (disclosed by U.S. Pat. No. 5,655,601). Flowing water systems include but are not limited to ground waters, effluent waters, and leachate waters.
For the purposes of the present invention, the term “construction” or “constructions” refers to structures such as buildings, tunnel structures, galleries, caverns, barrages, retention basins, hydroelectric power plants, earth dams, retaining walls, road construction works, slope drainage systems, water drainage channels, well containments or provisional construction pits. For the purposes of the present invention, constructions also are infrastructure facilities such as landfills (for municipal or commercial waste) including the drainage system passing through these, and also bridges and their drainage systems.
For the purposes of the present invention, standing water systems are, for example, standing waters in swimming pools or as a matrix in subterranean oil deposits.
Conditioning agents based on PSI are taken to mean, for the purposes of the present invention, PSI itself, its copolymers or its partial hydrolysates as are obtained, for example, from the reaction of aspartic acid with aspartic acid sodium salt according to WO 98/47964.
The flowing waters, e.g., ground waters, effluent waters, leachate waters produced in the above-mentioned constructions or operations, with utilization of the water properties, have differing contents of dissolved water constituents. These predominantly inorganic water constituents frequently cause hard deposits. On entry of, for example, ground waters or leachate waters into drainage systems, the physical conditions change so that the originally dissolved water constituents form hard, firmly adhering deposits, which can be present in amorphous or crystalline form. These deposits (encrustations) usually consist of calcium carbonate, magnesium carbonate, calcium sulfate (gypsum), silicates (SiO2), barium sulfate and iron oxides, all of which may be present in their hydrated form.
These hard, firmly adhering deposits diminish the outlet cross section, or in extreme cases completely close the outlet. As a result, the amounts of water produced can no longer drain off freely, and damming occurs, which can cause great damage.
In the swimming pool sector, for example, the water contained must be conditioned so that deposits do not occur on the pool walls or in pumps and filters. In the raw material exploration sector, e.g., oil extraction, the conditioning agents used there require high pressure stability and high thermal stability.
WO 94/19288 discloses a process for preventing the formation of deposits in a construction drainage system, which is characterized in that a conditioning agent which comprises a stabilizer for hardness constituents and a dispersant is added to the leachate water or ground water to be drained off.
Conditioning agents which are used are, inter alia, maleic anhydride polymers and copolymers.
U.S. Pat. No. 5,523,023 describes water treatment compositions based on polysuccinimide or its hydrolysates but not in combination with fatty acids or their derivatives.
U.S. Pat. No. 6,054,553 discloses water treatment compositions with a product containing recurring succinimide units but not in combination with fatty acids or their derivatives.
WO 95/16726 describes water conditioning agents with hydrolysated polymerisate of maleinimide.
EP 0 638 049 B1 and CH 689 452 A5 disclose processes for preventing cement-related deposits in a construction drainage system, the conditioning agent used being polyaspartic acid.
A disadvantage with the conditioning agents mentioned in the prior art is the fact that the hardness constituents/hardness stabilizers and dispersants used for this, owing to their high solubility in water, are readily transported away from the leachate water or ground water and therefore require permanent introduction of further conditioning agent.
Polyaspartic acid and certainly its salts, but also comparable compounds, e.g., polyacrylic acid, its copolymers and its salts, have the following disadvantages in practice:                In solid form they are highly hygroscopic substances, which can only be pressed to form slow-release tablets which are dimensionally stable in water having a high content of (inert) binder. This makes it difficult to have a high active compound content in the slow-release tablets.        The solubility of polyaspartates, polyacrylates or polyacrylate/poly-maleate copolymers in water is very high. Abrupt addition over a short period thus takes place. However, addition as uniform as possible would be expedient, which increases as far as possible in proportion to the pH (at very alkaline pH of the construction waters, usually the encrustation problem is also very great). This is difficult to achieve using the customary raw materials for slow-release tablets.        Polyaspartic acid and its salts, owing to their biodegradability, make possible immediate colonization by microorganisms which use these as substrate. The result is a biofilm on these slow-release tablets, which, in the vicinity of the tablet, leads to biofouling with corresponding corrosion problems with respect to concrete. Therefore, a substance which is only slightly water soluble and poorly biodegradable would be desirable, which can be considered as precursor for the actual active compound and releases this in low concentrations, but at sufficient concentrations in the context of scale inhibition. This would reduce the biofouling problems.        The thermal stability of polyaspartic acids is not always ensured at high temperatures.        
It is an object of the present invention, therefore, to develop a novel conditioning agent for conditioning standing and flowing water systems whose correlation of action between dispersing properties and hardness stabilizer properties and its thermal stability is considerably superior to the prior art. Such a novel dispersant would be of broad applicability, for example to protect heat-transfer surfaces, as occurring in industrial plants, such as water circulation systems of any type (cooling water circulation systems) or else machines using process water, e.g., washing machines. At the same time, such a conditioning agent would be universally usable in standing waters, e.g., swimming pools, but also in extreme situations such as squeeze operations.
This object is achieved by, and the present invention therefore relates to, conditioning agents for conditioning standing and flowing water systems, characterized in that these comprise an active content of polysuccinimide (PSI), its hydrolysate or its partial hydrolysate, and a process for preventing deposits in standing or flowing water systems, characterized in that a polysuccinimide-based conditioning agent is added to the standing water or to the leachate water, ground water, effluent water or flowing water to be drained off.